1.Field of the Invention
The present invention relates to the field of semiconductor device manufacturing, and more particularly, to a method of forming a uniformly doped layer angled with the respect to a substrate.
2.Related Art
Proper operation of a solid-state device depends, among other things, on the device geometry and the doping profile of the constituent semiconductor layers. Such solid-state devices are typically formed upon a generally planar substrate such as silicon. Impurities or dopants are introduced into semiconductor layers of the substrate to attain a desired doping profile, whereby, for instance, the conductivity of a layer may be enhanced or a pn-junction may be formed.
Certain semiconductor device geometries may require that dopants or impurities be introduced along a portion of a semiconductor region which is angled relative to the base substrate. Applying dopants uniformly along a vertical or angled semiconductor layer, however, is exceedingly difficult under current line-of-sight fabrication techniques.
For instance, during ion-implantation the depth of ion penetration and the uniformity of the resultant doping degenerate when the semiconductor layer is angled away from normal with respect to the bombarding ions. Thus, to dope vertical or angled junction sidewalls, complex tilting operations are required to maintain a perpendicular or near perpendicular angle of incidence.
Further limitations are encountered when doping regions of semiconductor devices which are difficult to access with a straight-line path from the ion source. For instance, narrow junction devices disposed in isolation tubs, e.g. trench or V-groove configurations, contain interior recesses and corners where ion-implantation techniques fail to achieve a sufficiently uniform doping profile.
Accordingly, a fabrication method for introducing dopants uniformly over angled semiconductor regions is desired.